An increase in intracellular calcium [Ca2+]i in podocytes is one of the major causes of their loss. Podocytopenia results in impaired glomerular filtration barrier (GFB) and proteinuria, characteristic for chronic kidney disease (CKD). Diabetic nephropathy (DN) is the leading cause of CKD. Key mediators of Ca2+ flux in the podocytes are ion channels of the transient receptor potential canonical (TRPC) family (1) (other sources were also reported). A number of stimuli can trigger an elevation of [Ca2+]i in the podocytes, including ATP and Angiotensin II (Ang II), and growing evidence suggests that both Ang II and ATP play a role in DN development. The goal of this study was to characterize mechanisms resulting in elevated [Ca2+]i in podocytes during DN. Dahl SS rats injected with streptozotocin (STZ-SS) and type 2 diabetic nephropathy (T2DN) rats were used as type 1 and 2 diabetes models. Rats were anesthetized with 2.5% isoflurane for kidney flush, and sacrificed using thoracotomy. Glomeruli were isolated from excised kidneys by differential sieving (2). Patch-clamp and imaging analyses were performed on podocytes of the glomeruli to assess calcium handling. Basal [Ca2+]i was enhanced in both STZ-SS and T2DN rats compared to respective controls (268.3 ± 30.9 nM in STZ-SS rats and 231.9 ± 20.2 nM in T2DN rats, vs Wistar (150.1 ± 10.8 nM) and untreated SS rats (131.1 ± 8.89 nM); p<0.01). Ang II application resulted in approximately 1.5 fold increase in calcium influx, and an elevation in the TRPC channels open probability in podocytes of STZ-SS compared to control rats (0.6 ± 0.1 vs 0.29 ± 0.12, p<0.01) (3). WB and IHC, along with the data obtained using TRPC modulators SKF 96365 and La3+, and knockout mice (4), was consistent with TRPC6 being the channel mediating this effect. Data are reported ± SEM, significance tested with ANOVA. Next, we assessed the effects of ATP on podocytes during DN. The response to ATP in Wistar rat podocytes was similar to what we reported for Sprague Dawley rats (EC50 = 10.7 ± 1.5 μM (5)). However, it was substantially enhanced in GK rats (diabetic but lacking pronounces DN), with dose-response curve shifted towards a potent activation with lower ATP concentrations. Importantly, calcium transient was further increased in T2DN, and dose-independent within the tested concentration range was shifted towards more potent activation by lower ATP concentrations. Western blotting revealed a significantly higher expression of ionotropic P2X7 and P2X4 receptors in the cortex of T2DN and GK strains compared to Wistar rats, and a decrease in the expression of metabotropic P2Y1 receptors. Taken together, these studies have a strong potential for advancing our understanding of calcium-mediated effects on podocytopenia in DN, and identification of new pharmacological targets to maintain podocyte integrity and function.